:root{--bg:#0d0f14;--surface:#151820;--surface2:#1c2030;--border:#252a3a;--accent:#5b8af0;--accent2:#38d9a9;--warn:#ff6b6b;--gold:#f0b429;--muted:#4a5270;--text:#d4daf0;--text-dim:#7b84a8;--heading:#fff;--code-color:#c0d9a8;--cm-bg:#1a1e2e;--cm-gutter:#151820;--overlay-bg:rgba(13,15,20,.92);--mono:'JetBrains Mono',monospace;--display:'Syne',sans-serif;--radius:8px;--ex-w:264px;--schema-w:212px}
[data-theme="light"]{--bg:#f0f2f7;--surface:#ffffff;--surface2:#e8ebf2;--border:#cdd2e0;--accent:#4a78e6;--accent2:#2a9d82;--warn:#d94444;--gold:#c48b15;--muted:#8892ad;--text:#2c3040;--text-dim:#5a6280;--heading:#1a1d28;--code-color:#2d6e3f;--cm-bg:#f8f9fc;--cm-gutter:#eef0f5;--overlay-bg:rgba(240,242,247,.94)}
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html,body{height:100%;background:var(--bg);color:var(--text);font-family:var(--mono);font-size:13px;overflow:hidden}

/* HEADER */
header{display:flex;align-items:center;gap:14px;padding:0 18px;height:48px;background:var(--surface);border-bottom:1px solid var(--border);flex-shrink:0;z-index:10}
.logo{font-family:var(--display);font-weight:800;font-size:15px;color:var(--heading);display:flex;align-items:center;gap:8px}
.logo-icon{width:26px;height:26px;background:linear-gradient(135deg,var(--accent),var(--accent2));border-radius:6px;display:flex;align-items:center;justify-content:center;font-size:13px}
.logo-sub{font-family:var(--mono);font-size:11px;color:var(--text-dim)}
.hdr-right{margin-left:auto;display:flex;align-items:center;gap:14px}
.prog-wrap{display:flex;align-items:center;gap:8px}
.prog-chip{font-size:11px;color:var(--text-dim);padding:3px 10px;border:1px solid var(--border);border-radius:20px;background:var(--surface2)}
.prog-chip strong{color:var(--accent2)}
.prog-bar{width:90px;height:5px;background:var(--border);border-radius:3px;overflow:hidden}
.prog-fill{height:100%;background:linear-gradient(90deg,var(--accent),var(--accent2));border-radius:3px;transition:width .5s ease;width:0%}
.status-dot{width:7px;height:7px;border-radius:50%;background:var(--warn);transition:background .4s}
.status-dot.ready{background:var(--accent2);box-shadow:0 0 6px var(--accent2)}
.status-lbl{font-size:11px;color:var(--text-dim)}

/* LAYOUT */
.app{display:flex;height:calc(100vh - 48px)}

/* EXERCISE SIDEBAR */
.ex-sidebar{width:var(--ex-w);flex-shrink:0;background:var(--surface);border-right:1px solid var(--border);display:flex;flex-direction:column;overflow:hidden}
.sidebar-hdr{padding:10px 14px 8px;font-family:var(--display);font-size:10px;font-weight:700;letter-spacing:1.5px;text-transform:uppercase;color:var(--muted);border-bottom:1px solid var(--border);display:flex;align-items:center;gap:8px}
.sidebar-hdr span{margin-left:auto;font-size:10px;color:var(--text-dim);text-transform:none;letter-spacing:0}
.ex-list{flex:1;overflow-y:auto;padding:6px 0}
.ex-list::-webkit-scrollbar{width:4px}
.ex-list::-webkit-scrollbar-thumb{background:var(--border);border-radius:2px}
.tier-lbl{padding:8px 14px 4px;font-size:10px;font-weight:600;letter-spacing:1px;text-transform:uppercase;display:flex;align-items:center;gap:7px}
.tier-pip{width:8px;height:8px;border-radius:2px;flex-shrink:0}
.ex-item{display:flex;align-items:center;gap:8px;padding:7px 14px;cursor:pointer;transition:background .12s;border-left:2px solid transparent}
.ex-item:hover{background:var(--surface2)}
.ex-item.active{background:rgba(91,138,240,.1);border-left-color:var(--accent)}
.ex-check{width:16px;height:16px;border-radius:50%;border:1.5px solid var(--border);flex-shrink:0;display:flex;align-items:center;justify-content:center;font-size:9px;transition:all .2s}
.ex-item.done .ex-check{background:var(--accent2);border-color:var(--accent2);color:#0d0f14;font-size:10px}
.ex-item-txt{font-size:11px;color:var(--text-dim);flex:1;min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.ex-item.active .ex-item-txt{color:var(--text)}
.ex-item.done .ex-item-txt{color:var(--muted);text-decoration:line-through;text-decoration-color:var(--muted)}

/* RIGHT SIDEBAR — Schema */
.schema-sidebar{width:var(--schema-w);flex-shrink:0;background:var(--surface);border-left:1px solid var(--border);display:flex;flex-direction:column;overflow:hidden}
.schema-hdr{padding:10px 14px 8px;font-family:var(--display);font-size:10px;font-weight:700;letter-spacing:1.5px;text-transform:uppercase;color:var(--muted);border-bottom:1px solid var(--border);display:flex;align-items:center;gap:6px;flex-shrink:0}
.cheat-btn{margin-left:auto;padding:3px 9px;background:var(--surface2);border:1px solid var(--border);border-radius:4px;color:var(--text-dim);font-family:var(--mono);font-size:10px;cursor:pointer;transition:all .15s;white-space:nowrap}
.cheat-btn:hover,.cheat-btn.active{border-color:var(--accent);color:var(--accent);background:rgba(91,138,240,.1)}
.schema-tree{flex:1;overflow-y:auto;padding:8px 0}
.schema-tree::-webkit-scrollbar{width:4px}
.schema-tree::-webkit-scrollbar-thumb{background:var(--border);border-radius:2px}
.tree-table{cursor:pointer;user-select:none}
.tree-table-name{display:flex;align-items:center;gap:7px;padding:5px 14px;font-size:12px;color:var(--text);transition:background .15s}
.tree-table-name:hover{background:var(--surface2)}
.tree-table-name .icon{font-size:11px;transition:transform .2s;color:var(--text-dim)}
.tree-table.open .tree-table-name .icon{transform:rotate(90deg)}
.tree-table-name .tname{color:var(--accent);font-weight:500}
.tree-cols{display:none;padding:2px 0 6px 28px}
.tree-table.open .tree-cols{display:block}
.tree-col{display:flex;align-items:center;gap:6px;padding:2px 14px 2px 0;font-size:11px;color:var(--text-dim)}
.tree-col .ctype{margin-left:auto;font-size:10px;color:var(--muted);font-style:italic}
.schema-actions{padding:8px;border-top:1px solid var(--border);display:flex;flex-direction:column;gap:5px;flex-shrink:0}
.btn-sm{width:100%;padding:6px 10px;background:var(--surface2);border:1px solid var(--border);border-radius:var(--radius);color:var(--text-dim);font-family:var(--mono);font-size:11px;cursor:pointer;text-align:left;transition:all .15s;display:flex;align-items:center;gap:7px}
.btn-sm:hover{background:var(--border);color:var(--text)}

/* CHEAT SHEET — overlay panel */
.cheat-overlay{position:fixed;top:48px;right:0;bottom:0;width:var(--schema-w);background:var(--surface);border-left:1px solid var(--border);display:none;flex-direction:column;overflow:hidden;z-index:50}
.cheat-overlay.visible{display:flex}
.cheat-overlay-hdr{padding:10px 14px 8px;font-family:var(--display);font-size:10px;font-weight:700;letter-spacing:1.5px;text-transform:uppercase;color:var(--muted);border-bottom:1px solid var(--border);display:flex;align-items:center;flex-shrink:0}
.cheat-close{margin-left:auto;background:none;border:none;color:var(--text-dim);cursor:pointer;font-size:16px;line-height:1;padding:0 2px;transition:color .15s}
.cheat-close:hover{color:var(--text)}
.cheat-sheet{flex:1;overflow-y:auto;display:flex;flex-direction:column;padding:4px 0}
.cheat-sheet::-webkit-scrollbar{width:4px}
.cheat-sheet::-webkit-scrollbar-thumb{background:var(--border);border-radius:2px}
.cs-section{border-bottom:1px solid var(--border)}
.cs-hdr{display:flex;align-items:center;gap:7px;padding:7px 12px;font-size:10px;font-weight:600;letter-spacing:.8px;text-transform:uppercase;color:var(--text-dim);cursor:pointer;transition:background .15s;user-select:none}
.cs-hdr:hover{background:var(--surface2);color:var(--text)}
.cs-hdr .cs-arr{font-size:9px;transition:transform .2s;flex-shrink:0}
.cs-section.open .cs-hdr .cs-arr{transform:rotate(90deg)}
.cs-body{display:none;padding:0 10px 8px}
.cs-section.open .cs-body{display:block}
.cs-code{font-family:var(--mono);font-size:10.5px;color:var(--code-color);background:var(--surface2);border:1px solid var(--border);border-radius:5px;padding:7px 9px;line-height:1.7;white-space:pre;overflow-x:auto;margin-top:5px}
.cs-code::-webkit-scrollbar{height:3px}
.cs-code::-webkit-scrollbar-thumb{background:var(--border)}
.cs-kw{color:#bd93f9}.cs-fn{color:#50fa7b}.cs-str{color:#f1fa8c}.cs-cmt{color:#6272a4}

/* ERD OVERLAY */
.erd-overlay{position:fixed;top:48px;left:0;right:0;bottom:0;background:var(--overlay-bg);backdrop-filter:blur(8px);display:none;flex-direction:column;overflow:hidden;z-index:60}
.erd-overlay.visible{display:flex}
.erd-overlay-hdr{padding:10px 18px 8px;font-family:var(--display);font-size:10px;font-weight:700;letter-spacing:1.5px;text-transform:uppercase;color:var(--muted);border-bottom:1px solid var(--border);display:flex;align-items:center;flex-shrink:0;background:var(--surface)}
.erd-controls{display:flex;align-items:center;gap:6px;margin-left:auto;margin-right:10px}
.erd-ctrl-btn{width:28px;height:28px;display:flex;align-items:center;justify-content:center;background:var(--surface2);border:1px solid var(--border);border-radius:4px;color:var(--text-dim);font-family:var(--mono);font-size:14px;cursor:pointer;transition:all .15s;line-height:1}
.erd-ctrl-btn:hover{border-color:var(--accent);color:var(--accent);background:rgba(91,138,240,.1)}
.erd-zoom-lbl{font-size:10px;color:var(--text-dim);min-width:36px;text-align:center}
.erd-body{flex:1;overflow:hidden;position:relative;cursor:grab}
.erd-body.dragging{cursor:grabbing}
.erd-canvas{transform-origin:0 0;position:absolute;top:0;left:0;display:flex;align-items:center;justify-content:center;min-width:100%;min-height:100%}

/* MAIN */
main{flex:1;display:flex;flex-direction:column;overflow:hidden;min-width:0}

/* EXERCISE DETAIL PANEL */
.ex-detail{flex-shrink:0;background:var(--surface2);border-bottom:1px solid var(--border);padding:12px 16px;display:none;flex-direction:column;gap:9px;max-height:210px;overflow-y:auto}
.ex-detail.visible{display:flex}
.ex-detail::-webkit-scrollbar{width:4px}
.ex-detail::-webkit-scrollbar-thumb{background:var(--border);border-radius:2px}
.ex-detail-top{display:flex;align-items:flex-start;gap:10px;flex-wrap:wrap}
.ex-tier-badge{font-size:9px;font-weight:600;letter-spacing:.8px;text-transform:uppercase;padding:3px 8px;border-radius:3px;white-space:nowrap;flex-shrink:0}
.ex-title{font-family:var(--display);font-weight:700;font-size:14px;color:var(--heading);flex:1;min-width:0}
.ex-nav{display:flex;align-items:center;gap:6px;margin-left:auto;flex-shrink:0}
.nav-btn{padding:4px 10px;background:var(--surface);border:1px solid var(--border);border-radius:4px;color:var(--text-dim);font-family:var(--mono);font-size:11px;cursor:pointer;transition:all .15s}
.nav-btn:hover{border-color:var(--accent);color:var(--accent)}
.ex-desc{font-size:12px;color:var(--text-dim);line-height:1.65}
.ex-desc strong{color:var(--text);font-weight:500}
.ex-desc code{color:var(--accent2);font-size:11px;background:rgba(56,217,169,.1);padding:1px 5px;border-radius:3px}
.ex-actions{display:flex;align-items:center;gap:8px;flex-wrap:wrap}
.hint-btn,.sol-btn{padding:4px 11px;background:transparent;border:1px solid var(--border);border-radius:4px;font-family:var(--mono);font-size:11px;cursor:pointer;transition:all .15s}
.hint-btn{color:var(--text-dim)}.hint-btn:hover{border-color:var(--gold);color:var(--gold)}
.sol-btn{color:var(--text-dim)}.sol-btn:hover{border-color:var(--accent);color:var(--accent)}
.hint-text,.sol-text{display:none;font-size:11px;line-height:1.6;padding:7px 10px;border-radius:5px;margin-top:2px}
.hint-text{color:var(--gold);background:rgba(240,180,41,.07);border:1px solid rgba(240,180,41,.2)}
.sol-text{color:var(--code-color);background:var(--surface2);border:1px solid var(--border);font-family:var(--mono);font-size:10.5px;white-space:pre;overflow-x:auto}
.hint-text.visible,.sol-text.visible{display:block}
.check-btn{padding:5px 16px;background:rgba(56,217,169,.12);border:1px solid rgba(56,217,169,.3);border-radius:var(--radius);color:var(--accent2);font-family:var(--mono);font-size:11px;font-weight:600;cursor:pointer;transition:all .15s;margin-left:auto;white-space:nowrap}
.check-btn:hover{background:rgba(56,217,169,.22);border-color:rgba(56,217,169,.55)}

/* EDITOR */
.editor-panel{flex-shrink:0;display:flex;flex-direction:column;border-bottom:1px solid var(--border)}
.panel-topbar{display:flex;align-items:center;gap:10px;padding:6px 14px;background:var(--surface);border-bottom:1px solid var(--border)}
.panel-lbl{font-size:10px;font-weight:600;letter-spacing:1px;text-transform:uppercase;color:var(--text-dim)}
.tab-pill{padding:3px 10px;border-radius:4px;font-size:11px;background:var(--surface2);border:1px solid var(--border);color:var(--text-dim);cursor:pointer;transition:all .15s}
.tab-pill.active{background:rgba(91,138,240,.18);border-color:var(--accent);color:var(--accent)}
.run-btn{margin-left:auto;display:flex;align-items:center;gap:7px;padding:6px 16px;background:var(--accent);border:none;border-radius:var(--radius);color:#fff;font-family:var(--mono);font-size:12px;font-weight:600;cursor:pointer;transition:all .15s}
.run-btn:hover{background:#7aaaf5;transform:translateY(-1px);box-shadow:0 4px 14px rgba(91,138,240,.4)}
.run-btn:disabled{opacity:.5;cursor:not-allowed;transform:none}
.shortcut{font-size:10px;color:var(--muted);padding:2px 5px;background:var(--surface2);border-radius:3px;border:1px solid var(--border)}
.editor-wrap{overflow:auto;min-height:130px;max-height:38vh;resize:vertical}
.CodeMirror{height:100%;min-height:130px;font-family:var(--mono)!important;font-size:13px!important;line-height:1.6!important;background:var(--cm-bg)!important}
.CodeMirror-scroll{min-height:130px}
.CodeMirror-gutters{background:var(--cm-gutter)!important;border-right:1px solid var(--border)!important}
.CodeMirror-linenumber{color:var(--muted)!important}

/* RESULTS */
.results-panel{flex:1;display:flex;flex-direction:column;overflow:hidden;min-height:0}
.results-topbar{display:flex;align-items:center;gap:10px;padding:6px 14px;background:var(--surface);border-bottom:1px solid var(--border);flex-shrink:0}
.results-meta{font-size:11px;color:var(--text-dim);margin-left:auto;display:flex;align-items:center;gap:10px}
.badge{padding:2px 8px;border-radius:10px;font-size:10px;font-weight:600}
.badge-ok{background:rgba(56,217,169,.15);color:var(--accent2)}
.badge-err{background:rgba(255,107,107,.15);color:var(--warn)}
.export-btn{padding:3px 10px;background:var(--surface2);border:1px solid var(--border);border-radius:4px;color:var(--text-dim);font-family:var(--mono);font-size:11px;cursor:pointer;transition:all .15s}
.export-btn:hover{border-color:var(--accent2);color:var(--accent2)}
.results-body{flex:1;overflow:auto}
.results-body::-webkit-scrollbar{width:6px;height:6px}
.results-body::-webkit-scrollbar-thumb{background:var(--border);border-radius:3px}
.state-empty{display:flex;flex-direction:column;align-items:center;justify-content:center;height:100%;gap:10px;color:var(--muted)}
.state-empty .big-icon{font-size:34px;opacity:.3}
.state-empty p{font-size:12px}
.error-box{margin:14px;padding:14px 16px;background:rgba(255,107,107,.08);border:1px solid rgba(255,107,107,.3);border-radius:var(--radius);color:var(--warn);font-size:12px;line-height:1.6;white-space:pre-wrap}
.success-msg{margin:14px;padding:12px 16px;background:rgba(56,217,169,.08);border:1px solid rgba(56,217,169,.25);border-radius:var(--radius);color:var(--accent2);font-size:12px}
.pass-banner{margin:14px;padding:14px 18px;background:rgba(56,217,169,.1);border:1px solid rgba(56,217,169,.4);border-radius:var(--radius);display:flex;align-items:center;gap:12px}
.pass-icon{font-size:22px}
.pass-text h3{font-family:var(--display);font-size:13px;color:var(--accent2);font-weight:700;margin-bottom:2px}
.pass-text p{font-size:11px;color:var(--text-dim)}
.pass-next{margin-left:auto;padding:6px 14px;background:var(--accent2);border:none;border-radius:var(--radius);color:#0d0f14;font-family:var(--mono);font-size:11px;font-weight:600;cursor:pointer;white-space:nowrap}
.pass-next:hover{opacity:.85}
.fail-banner{margin:0 14px 14px;padding:11px 16px;background:rgba(255,107,107,.06);border:1px solid rgba(255,107,107,.25);border-radius:var(--radius);color:var(--warn);font-size:11px;line-height:1.7;white-space:pre-wrap}
.fail-badge{display:inline-block;padding:2px 7px;border-radius:3px;background:rgba(255,107,107,.15);font-size:10px;font-weight:600;margin-bottom:4px}
.result-table-wrap{padding:12px}
table.rt{width:100%;border-collapse:collapse;font-size:12px}
table.rt thead th{position:sticky;top:0;background:var(--surface);padding:8px 12px;text-align:left;font-size:10px;font-weight:600;letter-spacing:.8px;text-transform:uppercase;color:var(--accent);border-bottom:1px solid var(--border);white-space:nowrap;z-index:2}
table.rt tbody tr{border-bottom:1px solid var(--border);transition:background .1s}
table.rt tbody tr:hover{background:rgba(91,138,240,.05)}
table.rt tbody tr:last-child{border-bottom:none}
table.rt td{padding:7px 12px;color:var(--text);max-width:260px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
table.rt td.null-val{color:var(--muted);font-style:italic}
table.rt td.num-val{color:var(--accent2)}
.history-list{flex:1;overflow-y:auto;padding:8px;display:flex;flex-direction:column;gap:6px}
.history-item{padding:8px 12px;background:var(--surface2);border:1px solid var(--border);border-radius:var(--radius);cursor:pointer;transition:all .15s}
.history-item:hover{border-color:var(--accent)}
.history-item .hi-q{font-size:11px;color:var(--text);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.history-item .hi-m{font-size:10px;color:var(--muted);margin-top:3px}
.resize-handle{height:5px;background:var(--border);cursor:ns-resize;transition:background .15s;flex-shrink:0;position:relative}
.resize-handle::after{content:'· · ·';position:absolute;left:50%;top:50%;transform:translate(-50%,-50%);font-size:8px;color:var(--muted);letter-spacing:2px}
.resize-handle:hover{background:var(--accent)}
.theme-toggle{width:32px;height:32px;border-radius:6px;border:1px solid var(--border);background:var(--surface2);color:var(--text-dim);font-size:15px;cursor:pointer;display:flex;align-items:center;justify-content:center;transition:all .15s;padding:0;line-height:1}
.theme-toggle:hover{border-color:var(--accent);color:var(--accent);background:rgba(91,138,240,.1)}
#loading-overlay{position:fixed;inset:0;background:var(--bg);display:flex;flex-direction:column;align-items:center;justify-content:center;gap:18px;z-index:100;transition:opacity .5s}
.spinner{width:36px;height:36px;border:3px solid var(--border);border-top-color:var(--accent);border-radius:50%;animation:spin .8s linear infinite}
@keyframes spin{to{transform:rotate(360deg)}}
.loading-logo{font-family:var(--display);font-weight:800;font-size:22px;color:var(--heading);display:flex;align-items:center;gap:10px}
@keyframes cfFall{0%{transform:translateY(-20px) rotate(0deg);opacity:1}100%{transform:translateY(100vh) rotate(720deg);opacity:0}}
.cf{position:fixed;border-radius:2px;animation:cfFall linear forwards;z-index:999;pointer-events:none}